None of the four are arbitration-eligible, but all four are expected to be signed back to Minor League deals in the next 24 hours, a source told MLB.com.

The moves will reduce the Royals' 40-man roster to 36, leaving them plenty of room for Winter Meetings transactions as well as possible Rule 5 Draft acquisitions.

Adam, 27, appeared in 31 games with Kansas City last year and posted a 6.12 ERA. Duenez, 22, had an .820 OPS in 80 games with Double-A Northwest Arkansas in 2018. Machado, 25, appeared in two games with the Royals in late 2017 and allowed nine runs in 3 2/3 innings (22.09 ERA).

Starling, the fifth overall pick in the 2011 MLB Draft, was limited to 20 games across three Minor League levels due to injury.